The present invention relates to a flat-plate lamination-type conductive polymer actuator and a flat-plate lamination-type conductive actuator device, as well as an operating method thereof.
With the social backgrounds like the falling birthrate and the aging proportion, there have been strong demands for machines, such as home-use robots, which are operated near a person or carry out jobs in cooperation with a person. Under these circumstances, from the viewpoints of flexible movements in response to complicated jobs or ensuring safety upon collision with a person, there are high expectations for artificial muscle actuators that have flexible characteristics like muscles of the human. For such artificial muscle actuators, various materials or control systems therefor, such as those using air pressure, have been proposed. In recent years, as one of these, there has been devised an actuator using a conductive polymer material.
As one example of the actuator using the conductive polymer material, there has been proposed an actuator that utilizes a bimorph-type deformation, as shown in FIGS. 16A, 16B, and 16C. As shown in FIG. 16A, this actuator has a structure in which a solid-state electrolyte molded body 151 is sandwiched between polyaniline films 150a and 150b provided as conductive polymer films. By turning a switch 152 on, an electric potential difference, which is set in a power supply 153, is applied between the polyaniline films 150a and 150b, so that, as shown in FIG. 16B, anions are inserted to the first polyaniline film 150b so that the film 150b is expanded, while anions are removed from the second polyaniline film 150a so that the film 150a is contracted; thus, a bimorph-type deformation is generated. In a case where the electric potential difference is reversed, as shown in FIG. 16C, deformation occurs in a direction reversed relative to that of FIG. 16B (see Patent Document 1 or the like).
In this structure, the deformations are generated by a difference in amount of displacement of the two conductive polymer films functioning as electrodes. On the other hand, a structure has been known in which, by forming the electrolyte holding layer as a liquid or gel-state substance, the two electrodes are prevented from giving effects to each other so as to achieve an actuator that exerts expanding and contracting deformations by taking out only the displacement of one of the conductive polymer films. In this case, with respect to the electrode not utilized for the deformation, it is not necessary to use the conductive polymer material, and a metal electrode is mainly used, and further alternatively, a conductive polymer material may be formed on the metal electrode.
Since this conductive polymer actuator can exert a stress corresponding to muscles at a comparatively low voltage in a range of from 1.5 V to 5.0 V, it is expected to be put into practical use as artificial muscles.
An ionic liquid, which is defined as a melted salt at a room temperature, is utilized as the liquid-state or gel-state electrolyte holding layer. The ionic liquid has drawn a public attention as a new functional liquid, and 1-butyl-3-methylimidazolium or bis (trifluoromethylsulfonyl) imide has been known as such a liquid. Since charges of cationic ions and anionic ions are non-localized, Coulomb forces exerted therebetween are small so that it may be maintained as a liquid at a room temperature. This liquid has a low vapor pressure, with hardly any evaporation loss, and is inflammable. Most liquids of this type are superior in heat and oxidation stability, and have a high lubricating performance. By applying this ionic liquid to an insulating sheet or by forming the ionic liquid itself into a gel, the electrolyte holding layer can be formed.
Moreover, it has been proposed that, since the conductive polymer material is formed into a film, the conductive polymer film is prevented from being buckled by being formed into a cylindrical shape so as to have rigidity. As shown in FIG. 17A, by alternately placing two types of conductive polymer films 60a and 60b having expanding and contracting properties in a circumferential direction so as to be coupled to the ends of the inside cylindrical member 61a and the outside cylindrical member 61b so as to intersect with each other; thus, by allowing one of the films to receive the load when the other film is made to expand, it is possible to provide rigidity. FIG. 17B shows one example of the layout of the conductive polymer films 60a and 60b in the circumferential direction. Moreover, as shown in FIG. 17C, a method is proposed in which this cylindrical member is formed by using conductive polymer materials 62a and 62b so as to increase the amount of displacement (see Patent Document 2 or the like).
Moreover, as shown in FIG. 18, in a structure in which conductive polymer films 70a and 70b are laminated so as to cross each other, they are connected to each other by a link mechanism 71 that can interchange one of displacements in the expanding direction to the other displacement in the contracting direction. It is therefore possible to provide an actuator that exerts a driving force in the expanding direction and rigidity in the contracting direction without necessity of applying a preliminary pressure (see Patent Document 3 or the like).
Patent Document 1: Japanese Unexamined Patent Publication No. 11-169393
Patent Document 2: Japanese Unexamined Patent Publication No. 2006-125396
Patent Document 3: Japanese Patent Publication No. 3817259
However, the actuator having the above-mentioned structure has the following issues.
In the method of Patent Document 1, since the bimorph-type deformation is utilized, it becomes difficult to expand the displacement by further laminating a conductive polymer film, or to freely alternate the expansion of a stress. In order to expand the displacement, the length of the conductive polymer film needs to be changed, and in order to expand the stress, the width of the conductive polymer film needs to be expanded; however, it is impossible to laminate a plurality of conductive polymer films. In particular, the structure of Patent Document 1 makes it difficult to achieve lamination.
The method of Patent Document 2 has a structure in which the conductive polymer films are formed into a cylindrical shape so as to have rigidity, with two types of films 60a and 60b having expanding and contracting properties in the circumferential direction of the cylindrical members 61a and 61b being alternately placed in the width direction thereof as shown in FIG. 17A. Thus being greatly different from a structure in which, as shown in FIG. 16A of Patent Document 1, the conductive polymer films are disposed to be made face to face in the thickness direction, this structure has an issue in that effective insertion and removal of ions through the electrolyte holding layer become difficult. Even supposing that not the layout as shown in FIG. 17B but a layout with higher density in the circumferential direction is made, the movements of ions between the adjacent conductive polymer films are lowered in efficiency, in comparison with the structure in which the polymer films are made face to face with each other. Consequently, it becomes difficult to output sufficient stress and displacement as an actuator. Moreover, in a structure shown in FIG. 17C, since there is given no specific description relating to a supporting member corresponding to the cylindrical member, buckling occurs in the conductive polymer films 62a and 62b, thereby failing to function as an actuator.
In the method of Patent Document 3, although, with respect to both of expansion and contraction, the driving force in the expanding direction and rigidity in the contracting direction are achieved without the necessity of applying a preliminary pressure, there are disadvantages in that the directions in which the driving force can be taken out are dispersed into two directions perpendicularly intersecting with each other, and in that the displacement is not increased even when the number of sheets of the conductive polymer films 70a and 70b to be laminated is increased.
It is therefore an object of the present invention to solve these issues and also to provide a flat-plate lamination-type conductive polymer actuator as well as a flat-plate lamination-type conductive polymer actuator device and an operating method thereof that exert rigidity and a driving force bidirectionally in a contracting direction and in an expanding direction and can expand displacement by lamination.